1. Field of Invention
The present invention relates to a surface light source device, image display and light path control plate which employ point-like light sources as light emitting source.
2. Related Art
So-called “collective-type-LED display” is known as a display utilizing a surface light source device employing a plurality of point-like light sources, being disclosed, for example, in Tokkai-Hei 6-104489 (Japan). According to the disclosure, a casing accommodates a substrate on which a plurality of light emitting diodes (LEDs) are mounted as point-like light sources like a matrix. Lenses are disposed immediately in front of light emitting faces of the LEDs. The lenses have lower faces providing flat faces and upper faces providing convergent lens structures convergence of which is higher in a upper-lower diction as compared with in a lateral direction.
This display is subject to problems such that light for displaying involves glaring or blurring occurs between pixels because light emitted from LED is converged. In such conventional displays, directivity of light emitted from LED is only modified as to be converged, with the result that viewing angle is narrow and image clearness falls when viewing direction is deviated from a frontal direction of the display screen. This problem is serious, in particular, for large screen size displays.